THE football thugs who caused mayhem outside Ibrox at the weekend were celebrating a “top boy’s” 50th birthday.

Aberdeen casuals had travelled to Glasgow to fight against Rangers hooligans and have a party for one of their founding members.

Many of them were veterans from football violence’s 1980s heyday.

Around 120 seasoned thugs from the Aberdeen Soccer Casuals clashed with Rangers fans and casuals from their Inter City Firm on Saturday.

A source said: “The older Aberdeen boys were there because it was one of their top boys’ 50th birthday.”

A group of 20 Germans – fans of Dynamo Berlin who have a link-up with Aberdeen – were caught up in the 15 minutes of madness.

The violence broke out at Ibrox subway station about 20 minutes before kick-off. About 40 ASC thugs steamed out of the station and into fans heading to the game.

Rival hooligans threw punches and hurled bottles and pieces of wood.

Cops drew batons and used CS spray to try to stop trouble described by one fan as the “worst fighting” he had ever witnessed at football.

Mounted officers were brought in to get the situation under control. But the neds gave cops the slip.

A male officer broke his hand and a female officer suffered a leg injury during the brawl.

It had been rumoured that Tottenham casuals had travelled up for the battle – but a source denied that.

He added: “A large number of Aberdeen boys turned out because it was the guy’s 50th and it coincided with an away game against Rangers.

“He was one of their founding members way back in the early 80s. It was always going to kickoff with a mob like that on the streets of Glasgow.

“The fight with Rangers wasn’t prearranged as there would have been greater numbers of the ICF.”

Formed in 1980, ASC were Scotland’s first casual mob. Shedding the skinhead image, they wore designer gear such as Stone Island, Lacoste, Fila and Ellesse.

On Saturday, the yobs boarded a subway train in the west end of Glasgow to avoid being split up by police monitoring stations in the city centre. About 300 Aberdeen fans had been boozing at The Rock in Hyndland before the game.

Manager Steven Samson said: “It was mayhem but not in a bad way.

“We got a call on the Tuesday from some fans who were bringing a coach, so we made all the necessary arrangements and cordoned off an area for locals.

“There were three coaches of fans and in the end we had to stop people coming in.

“We had stewards, and police were waiting in two vans nearby and kept coming in and out every half-hour to check everything was all right.”

A former Rangers thug blamed a police blunder for the flare-up.

Sandy Chugg – who tried to set up fights during Scotland’s France 98 World Cup adventure – said serious questions would be raised at Strathclyde Police HQ.

Reformed Chugg, 39, said: “Back when casuals were at their height, this type of thing could happen any Saturday but those days are long gone.

“There was always a cat-and-mouse game, trying to give police the slip. Now you can’t move without CCTV tracking every detail.

“Anyone identified as being an organiser will have a file with the cops and they might well have their phone tapped, too.

“Any movements on public transport will be monitored.

“I can’t believe a group of around 50 Aberdeen casuals could be allowed to board a subway train, take it to the busiest station and come out unchallenged.

“Someone will be getting their a*** kicked – it’s a major blunder.”

Yesterday, the chief of the police division covering Ibrox defended their operations on Saturday.

Chief Superintendent Andy Bates said: “Unfortunately, situations such as these can flare up quickly.